An Oklahoma judge on Friday put off deciding whether to accept a man's request to plead guilty to first-degree murder in the beheading of a co-worker, as a death sentence would still be possible.

Alton Nolen reiterated his desire to plead guilty and die by lethal injection after Cleveland County District Judge Lori Walkley asked a series of questions to assess whether he understood the charges against him stemming from the September 2014 attack at the Vaughn Foods plant in the Oklahoma City suburb of Moore.

"I'm being (held) captive to the disbelievers of Allah, the one and only God," Nolen, who converted to Islam shortly before the attack, told the judge, declining to take the stand when delivering his testimony. "It's part of my religion that when death faces you, you do not back down."

Responding to a question from one of his attorneys, who argue that he's not mentally competent enough to enter a plea, Nolen said, "I'll say it again. I'm here today to plead guilty."

Citing questions raised by a psychologist who evaluated Nolen at the request of his attorneys, Walkley said she wanted to be sure Nolen "knowingly and voluntarily" entered a guilty plea before she'll agree to accept it. She said she would announce her decision on Aug. 12.

If Nolen is allowed to plead guilty, there would be a separate hearing to determine his sentence.

Nolen, 31, told Walkley on Friday that he wants to plead guilty to three of the six charges stemming from the attack at the Vaughn Foods plant in Moore, including the first-degree murder charge and two assault charges. At a February hearing in which he also asked to plead guilty, Nolen told Walkley that he would only accept a death sentence, not one of the lesser sentences the charge carries of life in prison with or without the possibility of parole.

Walkley reminded Nolen repeatedly that if he pleaded guilty and waived his right to a jury trial, the decision to sentence him to death or life in prison would be up to the judge, not the defendant.

Prosecutors, who are seeking the death penalty, say Nolen had just been suspended from his job at the plant when walked into an administrative office and attacked Hufford, severing her head. They say he also stabbed and wounded another co-worker before a company executive shot him.

At a January hearing, Gary Hazelrigg, who was Vaughn's customer service manager at the time, testified that Hufford was in his office when Nolen came in and grabbed her from behind while holding a butcher knife.

"In no more than a second or two, the man pulled her forehead toward him and made a vicious cut across her throat with the knife," said Hazelrigg. He said Nolen then threw Hufford to the floor, sat on top of her and sawed at her throat.

"At some point he jumped up and turned on me with the knife in hand," Hazelrigg said. He said he picked up a chair to keep the distance between them and escaped into a locked room.

Authorities say Nolen ran down a hallway and attacked another employee, Traci Johnson, before the plant's chief operating officer, Mark Vaughan, shot him with a rifle. Vaughan is also an reserve sheriff's deputy